In electronic circuitry, it is frequently necessary to measure the relative phases of two different signals, and many circuits are known for performing this measurement. With the recent increase in the use of digital circuitry, one common method of measuring the phase of two analog signals is to pass each of the signals through a limiting amplifier to convert the signals to digital signals and then measure the relative phase of the two limited signals using digital circuitry. Where very precise phase measurements are required, offset voltages in the limiting amplifiers may introduce asymmetrical output signals which result in errors in the phase measurement.
The present invention includes a circuit for measuring the relative phase of two sinusoidal signals. In the present invention, the analog waveforms are applied to limiting amplifiers which provide digital output signals. The digital output signal representative of each analog input signal is applied to digital circuitry which provides an analog voltage representative of the phase between the two input signals. The digital circuitry compensates for any offset errors which may be introduced by the limiting amplifiers and provides an analog output representation of the phase which is unaffected by offset errors in the limiting amplifiers. The circuitry is capable of measuring relative phases over a 360 degree range.